In the field where it is required to initiate the remote opening and closing of valves, actuators are used. In some applications, it is necessary for the valve end travel positions to be adjusted or limited. In other words it is sometimes necessary to control the degree of opening and closing of valves. In the field, the devices which limit the degree of opening and closing of valves by an actuator are called in one instance travel stops.
A typical travel stop is a paddle rotatably mounted on an exposed shaft of an actuator, which has two adjustable bolts connected to the actuator, which in turn restrict the rotational movement of the paddle in one direction by adjusting the bolt position. When the exposed shaft of the actuator rotates which in turn rotates the paddle, one side of the paddle abuts against one of the bolts. Applicant has found that this arrangement creates an unbalanced load on the exposed shaft which may in time lead to premature wear in the bearings and leakage of the seals in the actuators.
Applicant has also found that this arrangement may interfere with mounting of accessories on the actuator, such as limit switches, or the like.
Another typical design consists of a stroke adjuster connected to the ends of an actuator through the end caps, which involves the penetration of the pressure boundary in the actuator itself. This penetration could lead to potential pressure leak paths resulting in the failure of the actuator. Furthermore, applicant has found that this particular configuration cannot be easily retrofitted in the field without dismantling the actuator itself and without replacing the end caps of the actuator with end caps to conform with the stroke adjuster arrangement as well. This may become costly to the user.
It is therefore an object of the invention to provide an external rotation limiter for a valve actuator which will reduce the side loads on the shaft which in turn reduces the chance of wearing of the seals in the actuator.
It is also another object of the present invention to provide a rotation limiter for a valve actuator which can be easily retrofitted on an actuator incorporating existing bolt holes thereon, thus eliminating the need to purchase accessories to install the device.
It is yet another object of the present invention to provide a rotation limiter for a valve actuator which does not penetrate the pressure boundary of the actuator thus reducing the possibility of pressure leaks.
It is yet another object of the present invention to provide a rotation limiter for a valve actuator which will not interfere with other accessories on the valve actuator.
It is yet another object of the present invention to provide a rotation limiter for a valve actuator such that the sum of moments and forces on the shaft is substantially nil.
It is yet another object of the present invention to provide a rotation limiter for a valve actuator that is unidirectional.
It is yet another object of the present invention to provide a rotation limiter for a valve actuator that is bidirectional.
Further and other objects of the invention will become apparent from the following summary of the invention and detailed description of embodiments of the invention.